U.S. patent application number 10/407069 was filed with the patent office on 2004-10-07 for microfuel cells for use particularly in portable electronic devices and telecommunications devices.
Invention is credited to Bergamasco, Jean-Lue, Curlier, Patrick, Gauthier-Manuel, Bernard, Marechal, Manuel, Pichonat, Tristan, Sanchez, Jean-Yves.
Application Number | 20040197613 10/407069 |
Document ID | / |
Family ID | 32990274 |
Filed Date | 2004-10-07 |
United States Patent
Application |
20040197613 |
Kind Code |
A1 |
Curlier, Patrick ; et
al. |
October 7, 2004 |
Microfuel cells for use particularly in portable electronic devices
and telecommunications devices
Abstract
The invention relates to a miniature fuel cell powered by a
hydrocarbon fuel making heavy use of micro-technologies in making
and assembling the sub-assemblies of the cell. Relative to the
prior art, the main innovation consists in using a semiconductor
oxidised and made porous in predetermined areas, to receive an
electrolytic polymer allowing the composition of the proton
exchange membrane necessary for the fuel cell to operate.
Inventors: |
Curlier, Patrick; (Boutigny,
FR) ; Bergamasco, Jean-Lue; (Paris, FR) ;
Pichonat, Tristan; (Besancon, FR) ; Marechal,
Manuel; (Saint Martin D'Heres, FR) ; Gauthier-Manuel,
Bernard; (Besancon, FR) ; Sanchez, Jean-Yves;
(Saint Ismier, FR) |
Correspondence
Address: |
BLAKELY SOKOLOFF TAYLOR & ZAFMAN
12400 WILSHIRE BOULEVARD
SEVENTH FLOOR
LOS ANGELES
CA
90025-1030
US
|
Family ID: |
32990274 |
Appl. No.: |
10/407069 |
Filed: |
April 4, 2003 |
Current U.S.
Class: |
429/413 ;
429/494; 429/506; 429/515; 429/516; 429/524 |
Current CPC
Class: |
H01M 8/1044 20130101;
H01M 8/1023 20130101; H01M 8/1032 20130101; H01M 8/1011 20130101;
H01M 8/1025 20130101; H01M 8/106 20130101; Y02P 70/56 20151101;
H01M 8/1039 20130101; H01M 8/1037 20130101; H01M 8/1027 20130101;
H01M 8/1062 20130101; Y02E 60/523 20130101; H01M 8/1067 20130101;
H01M 8/1072 20130101; H01M 8/1074 20130101; Y02P 70/50 20151101;
Y02E 60/50 20130101; H01M 8/1097 20130101 |
Class at
Publication: |
429/014 |
International
Class: |
H01M 008/04 |
Claims
1. Fuel cell including a complex (3c) comprising an oxygen
electrode (8a) and a fuel electrode (8b) surrounding a membrane
(11) composed of a microporous medium impregnated with an
electrolytic polymer, said cell being fed by an air source and a
fuel source, wherein the microporous medium is made of a
semiconductor material, this microporous medium having a plurality
of microporous cell elements delimited between each other by
recesses and in that the electrode and membrane complex comprising
a plurality of cell elements is encapsulated between two
exchanger/distributor components, one of these components
comprising means for receiving a fuel cartridge.
2. Cell according to claim 1, wherein the microporous medium is
made of oxidised silicon.
3. Cell according to claim 1, wherein the electrolytic polymer is
Nafion.RTM. 117 or an equivalent polymer.
4. Cell according to claim 1, wherein the electrodes (8a and 8b)
are composed of platinum, gold or a conductive mask obtained by
thin layer deposition techniques.
5. Cell according to claim 1, wherein the electrodes are made of a
highly conductive metal.
6. Cell according to claim 1, wherein the electrodes (8a and 8b)
are coated with a catalyst composed of Platinum or
Platinum/Ruthenium.
7. Cell according to claim 1, wherein the fuel is an alcohol, like
methanol.
8. Cell according to claim 7, wherein the fuel is methanol diluted
in water.
9. Cell according to claim 1, wherein the membrane is composed of a
stack of basic membranes separated by Palladium type metal layers
permeable to H.sup.2 protons and impermeable to Methanol so as to
improve the seal tightness of the membrane to Methanol.
10. Use of the cell according to one of the previous claims in
telecommunications devices.
11. Use of the cell according to one of the previous claims in
automobile equipment.
12. An electrolytic membrane of a fuel cell comprising a
microporous silicon membrane wherein channels comprise a proton
conductive material.
13. A membrane according to claim 12, wherein the proton conductive
material comprises a polymeric material.
14. A membrane according to claim 13, wherein the polymeric
material is selected from the group consisting of perfluorinated
polyelectrolytic polymers bearing a sulfonic function and
perfluorinated polyelectrolytic polymers bearing a carboxylic
function.
15. A membrane according to claim 13, wherein the polymeric
material is a polyelectrolytic polymer with an aromatic skeleton
selected from the group consisting of polysulfones,
polyethersulfones, polyether-ether-ketones, polyphenylene oxides
and polyphenylenesulfides.
16. A membrane according to claim 15, wherein the aromatic skeleton
comprises at least one ionic group selected from the group
consisting of sulfonic groups, phosphonic groups and carboxylic
groups.
17. A membrane according to claim 16, wherein the aromatic skeleton
comprises several different ionic groups.
18. A membrane according to claim 12, wherein the proton conductive
material comprises a monomer or an oligomer material that is
cross-linked once in the channels.
19. A membrane according to claim 18, wherein the monomer or
oligomer material comprises a polysiloxane skeleton bearing at
least one sulfonic function.
20. A membrane according to claim 18, wherein the monomer or
oligomer material is added with at least one ionic group selected
from the group consisting of, sulfonic groups, phosphonic groups
and carboxylic groups once in the channels.
21. A membrane according to claim 12, wherein the material
comprises molecules bonded to the inner surface of the
channels.
22. A membrane according to claim 21, wherein the proton conductive
molecules comprise bonded monomers.
23. A membrane according to claim 22, wherein the monomers comprise
a derivative selected from the group consisting of silanes and
silicon compounds.
24. A membrane according to claim 23, wherein the monomer has a
formula selected from the group consisting of
Si(Cl).sub.n(CH.sub.2).sub.x(C.sub.- 6H.sub.5).sub.4-n and
Si(OR).sub.n(CH.sub.2).sub.x(C.sub.6H.sub.5).sub.4-n- , wherein x
can assume the values of 0 to 8 but preferably from 0 to 4, n can
vary between 1 and 3, preferably between 2 and 3, R is an alkyl
group of the general formula: C.sub.nH.sub.2n+1.
25. A membrane according to claim 24, wherein the channels comprise
other monomers selected from the group consisting of
Si(Cl).sub.nR.sub.4-n' and Si (OR).sub.nR.sub.4-n', wherein R' can
be an alkyl CnH2n+1 or an alkenyl C.sub.nH.sub.2n-1.
26. A membrane according to claim 21, wherein the monomer molecules
are bonded and cross-linked.
27. A membrane according to claim 12, wherein the channels have a
diameter between 1 and 10 nm.
28. A membrane according to claim 12 comprising a thin layer of
platinum on the two surfaces of the silicon porous membrane.
29. A membrane according to claim 28, wherein the layer of platinum
is from 1 to 2 nm thick.
30. A membrane according to claim 12, wherein the channels at the
centre of the membrane have a small diameter and the channels on
the outer surface of the membrane have a larger diameter.
31. Method for making a microporous silicon membrane of a fuel cell
comprising a proton conductive material in channels defining the
permeability of the membrane, comprising the steps of: using a
wafer of doped and oxidized silicon; making of the porous silicon
by anodisation in a solution; introducing a proton conductive
material in channels made by the anodisation.
32. Method according to claim 31, wherein it comprises the step of
introducing a sulfonated polymer in the channels.
33. Method according to claim 32, wherein the polymer solutions of
5 to 20 mass-% by weight in water/alcohol solvents are introduced
in several steps, and wherein, after passage of each solution, the
porous material is heated to eliminate the alcohols.
34. Method according to claim 31, wherein the sulphonation is done
once the material is in the channels, the reagent enabling
introduction of the ionic group on the material being introduced
into the porosities after the filling of the porosity using the
polymer solution.
35. Method according to claim 31, wherein it comprises the step of
introducing a monomer or oligomer in the channels.
36. Method according to claim 35, wherein the a monomer or oligomer
is in the form of acid or alkali, in concentrated solution or in
molten form.
37. Method according to claim 35, wherein the monomer or oligomer
is introduced in the channels in the presence of an initiator
enabling post-polymerization after filling the porosity.
38. Method according to claim 37, wherein the cross-linking is
induced by the phenomena selected from the group consisting of
heating above the temperature of decomposition of the initiator, UV
irradiation and electron bombardment.
39. Method according to claim 35, wherein the cross-linking is done
after the filling of the channels, the reagent enabling
introduction of the ionic group being introduced into the porosity
after the material.
40. Method according to claim 35, wherein it comprises the step of
bonding the molecules of the material to the inner surface of the
channels.
41. Method according to claim 40, wherein the introducing of the
conductive material is made by impregnation by capillarity.
42. Method according to claim 40, wherein the monomer or oligomer
comprises at least an aromatic ring.
43. Method according to claim 42, wherein, after the bonding, total
or partial, of the monomer with the surface, the sulfonation
reagent enabling substitution of the at least aromatic ring by at
least a sulfonic group is introduced.
44. Method according to claim 42, wherein it comprises the step of
introducing into the porosity monomers selected from the group
consisting of Si(Cl).sub.nR.sub.4-n' and Si(OR).sub.nR.sub.4-n'
wherein R' can be an alkyl CnH2n+1 or an alkenyl
C.sub.nH.sub.2n-1.
45. Method according to claim 44, wherein, after the bonding, total
or partial, of the monomer with the surface, the sulfonation
reagent enabling substitution of the at least aromatic ring by at
least a sulfonic group is introduced.
46. Method according to claim 31, wherein anodisation is processed
in a solution comprising hydrofluoric acid/water/ethanol.
47. Method according to claim 31, wherein anodisation is added with
an etching of the rear surface of the membrane, so as to allow the
piercing of all the channels.
48. Method according to claim 47, wherein the etching is a plasma
reactive etching.
49. Method according to claim 31, wherein before introducing the
conductive material, the channels are then made hydrophilic by
fixing OH groups on the inner surface of the channels.
50. Method according to claim 49, wherein the steps to make the
channels hydrophilic are: putting the membrane in a solution
containing 80% of sulphuric acid and 20% of hydrogen dioxide during
around 60 minutes; putting the membrane in a container where each
surface is exposed to ultraviolet rays and an ozone flux during
around 10 minutes.
51. Method according to claim 31, wherein the material comprises
molecules selected from the group consisting of silanes and silicon
compounds.
52. Method according to claim 40, wherein before the bonding of
molecules, OH groups are fixed to the inner surface of the
channels.
53. Method according to claim 31, wherein the membrane is put in an
acid silane solution to a concentration of 1% during 60
minutes.
54. Method according to claim 40, wherein monomers and/or polymers
are added in the channels after the bonding of the first
molecules.
55. Method according to claim 54, wherein the monomers and/or
polymers are cross-linked to each other and/or to the bonded
molecules.
56. Method according to claim 31, wherein the surfaces of the
membrane are coated by a catalyst.
57. Method according to claim 56, wherein the catalyst is a thin
layer of platinum, which is coated by cathodic spraying.
58. Method according to claim 40, wherein the molecules are
cross-linked between each other once in the channels.
59. Use of the cell membrane according to one of claims 12 to 30 in
telecommunication devices.
Description
BACKGROUND OF THE INVENTION
[0001] The present intervention relates to the field of microfuel
cells for use particularly in portable electronic devices,
automobile equipment and telecommunications devices.
[0002] Miniaturisation of numerous devices, such as mobile phones,
computers, personal digital assistants, digital cameras, etc,
provokes the need for energy sources of small dimensions and high
capacity.
[0003] The current solution is the use of batteries. However, the
life span of batteries is short, and the need for a recharge of the
battery is cumbersome. Indeed, an electrical plug is sometimes hard
to find, it is hard to use the portable device during the charging.
Furthermore, the batteries are hard to recycle and are an
environmental hazard. Plus, the batteries are expensive to
make.
[0004] Some intents of using fuel cells have been made.
[0005] Fuel cells convert the chemical energy stored in a fuel into
electrical energy by an electrochemical process which consists in
causing a gas or a liquid to react in the presence of an
electrolyte, electrodes and a catalyst. More exactly, the catalyst
induces the release of electrons from the fuel which circulate from
one electrode to the other via an external circuit incorporating
the charge while the protons pass through the electrolytic material
separating the two electrodes.
[0006] Unlike a battery, a fuel cell does not lose its charge or
need to be recharged; it operates so long as a fuel and an oxidant
are supplied continuously to the cell, by intake from outside. In a
standard fuel cell, hydrogen atoms lose their electron at the anode
and combine with other electrons and with oxygen from the air at
the cathode. Water is the only product generated from the process
and the electrodes are not consumed. Conversely, with batteries the
electrodes themselves constitute the material participating in the
chemical reaction. Compact lithium batteries designed for portable
electronic appliances provide an output voltage of about 3 to 4
volts, whereas a basic fuel cell element is not able to develop
more than 1 volt. Given its higher power and specific volume, the
fuel cell is able to contain more energy in the same volume and the
required output voltage can be obtained by putting several basic
cell elements in series. Additionally, the fuel cell can be used
almost immediately after being recharged with fuel whereas
secondary batteries of the lithium-ion type require an
immobilisation phase in respect of recharging dependent on their
technology.
[0007] Miniaturising fuel cells must make it possible to conserve
sufficient power and energy, (i.e. low internal impedance), to
attain a volume and a mass compatible with their use, and must
allow the implementation of an efficient fuel which is able to be
diffused in a standard distribution system. Lastly, the microcell
manufacturing process must comprise a restricted number of
operations compatible with a low production cost.
[0008] The membranes of current microcells are constituted by a
first polymer generally in the form of a microporous film
impregnated with a second polymer. The second polymer--typically
Nafion 117 .RTM.--acts as the electrolyte and allows the transport
of protons. The solid flexible polymer structure is coated on its
two surfaces with a unit constituted by a series of thin layers the
function of which is to catalyse the oxidation of the fuel, to
transport the electrons to the anode or the cathode, to transport
the protons to the membrane, and to provide a maximum tightness
seal in respect of liquids (see WO 98/31062). Current microcells
are constituted by a stack of membranes and electrodes which are
compressed in order to try to guarantee seal tightness.
[0009] Nafion 117.RTM. is costly. Furthermore, it needs water to
operate. Therefore, cells using Nafion 117.RTM. impregnated
membranes according to the state of the art are slow to start. On
top of that, the transverse leaks are impossible to control. It is
hard as well to get small devices with this material.
[0010] Plus, in these devices, the water contained in the membrane
which is required for the transport of the protons, evaporates
under the thermal stresses of the operation or the environment.
Additionally, the liquid fuel tends to filter through the membrane,
which reduces the efficiency of the cell. Lastly, the techniques of
assembly used to manufacture current microcells are highly
hybridised and require a great number of handling operations.
[0011] WO 00/69007 discloses a fuel cell that uses a silicon
membrane. The document discloses a fuel cell that uses a porous
silicon wafer which is called "wafer silicon membrane". However,
the membrane disclosed in the document is not used as the
electrolyte membrane of the fuel cell, but as an electrode.
Therefore, the fuel cell always has to use a proton exchange
membrane based on a polymer film.
[0012] Another solution proposed is the making of dynamic
membranes. Such examples of membranes are disclosed in WO 01/15
253. The membranes in this document are in liquid state and make
the miniaturization difficult.
[0013] The cell proposed in the context of the present intervention
allows all these drawbacks to be overcome.
a. BRIEF SUMMARY OF THE INVENTION.
[0014] The subject of the present intervention is a cell including
an oxygen electrode and a fuel electrode framing a membrane
composed of a microporous medium impregnated with an electrolytic
polymer, said cell being fed by an air source and a fuel source.
The microporous medium is composed of a semiconductor.
[0015] The semiconductor used as the solid medium of the
electrolytic membrane makes it possible to control the porosity
percentage and the pore dimensions, which are thus able to
constitute a very effective barrier to the water molecules included
in the membrane and to the fuel molecules. Moreover, the use of a
semiconductor provides surfaces of quality for depositing the
electrodes.
[0016] Using a semiconductor also allows processes to be
implemented which call on micro-technologies--in respect of
machining and depositing metal films--and on conventional bounding
techniques. Micro-technologies allow multilayer metal depositions
of optimised thickness to be obtained. Integration of the
electronic circuits of management of the energy is possible.
[0017] The industrial techniques allow a low cost of production.
The potential for mass micro-production from wafers made of
semiconductor materials allows a restricted number of hybridisation
operations to be implemented compatible with low production
costs.
[0018] Microcells according to the invention can be manufactured in
series using the automated means of the semiconductor industry. The
size and geometrical layout of the cell elements can be easily
adapted. Lastly microcells manufactured in this way can be directly
integrated into powered electronics.
[0019] Using an electrolytic membrane comprising a semiconductor
medium allows the internal impedance of the cell to be reduced
thanks to the reduced membrane thickness. Additionally a perfect
fuel tightness, and seal tightness against the water contained in
the membrane is guaranteed, so that long-term operation of the cell
in a fluctuating environment is conceivable.
[0020] The polymer membrane has to be thick enough to keep good
mechanical properties (typically 7 mill inches (178 .mu.m) for
Nafion 117.RTM.). On the contrary, porous silicon allows reduction
of the thickness to a dimension as small as 40 .mu.m.
[0021] Moreover, the surfaces of the polymer membrane are even.
That is why the exchange surface is only equal to the surface of
the membrane. On the contrary, the use of porous silicon allows an
irregular and rough surface. This provides a higher exchange
surface.
[0022] The semiconductor is preferably silicon. It is to advantage
used in the form of wafers with standard dimensions 3' or 5'.
[0023] The semiconductor is oxidised to make it electrically
insulating and porous in predetermined areas. The porosity is
adapted to the molecular size of the electrolytic polymer. It is
impregnated with a conventional electrolytic polymer which provides
the diffusion of the protons in the membrane. The electrolytic
polymer is for example Nafion.RTM. 117 or a polymer of similar
ionic conductivity.
[0024] The electrodes are deposited on the surface of the
semiconductor. They are to advantage constituted by a metal
conventionally used in electrochemical reactions, permeable to
protons, preferably gold or platinum or a conductive mask.
[0025] The thickness of the catalyst/electrode complex is optimised
in such a way as to ensure the efficiency of the cell and to
guarantee the fuel tightness. The seal tightness may be improved by
retaining a membrane composed of a stack of basic membranes
separated by metal layers permeable to protons and impermeable to
fuel.
[0026] On the hydrogen fuel side, the electrode is coated with a
catalyst like Platinum or Ruthenium and Palladium. According to one
embodiment, the catalyst material is deposited in a thin layer on
the electrode. To advantage, the catalyst material is deposited in
several thin layers the granular structure of which may be
different. According to another embodiment, the fuel electrode is
coated with a layer of Palladium-doped porous silicon increasing
the actual surface of the catalysis.
[0027] The fuel is preferably an alcohol, such as methanol diluted
in water necessary for the chemical reaction. Low dilutability
guarantees high specific energy. Conversely, the low dilutability
is not favourable to limiting the poisoning of the catalyst by the
CO generated by the chemical reaction.
[0028] The cell according to the invention is to advantage equipped
with exchanger-distributors for the fuels, oxidants and gases and
energy generated by the electrochemical reactions. On the fuel
side, evacuating the gases, particularly CO.sub.2 and saturated CO,
is designed as a function of the supply connections of an
interchangeable reservoir.
[0029] Because of the low kinetics of the gases generated by the
electrochemical reaction, and in order to limit the dimensions of
the exchangers responsible for responding to the thermal management
of the cell, a micro-pump of MEMS technology may be used. In the
same way, a micro-pump which may be of similar technology will be
used to advantage in order to ensure the management of the
circulation of the air and water. This contribution of active
Microsystems helps in the miniaturisation of the device.
[0030] Given the moderate efficiency of the device (between 50 and
60%), the condensed part of the water generated by the reaction may
be evaporated following its passage through an exchanger near the
active cell elements.
[0031] The exchangers may to advantage be composed of glass or
silicon or carbon or a technical plastic.
[0032] Cells according to the invention may be equipped with a
heating device in the event of the water contained in the membrane
freezing. This device is to advantage located on the periphery of
the cell elements in the non-thinned out part of the oxidised
silicon. It is constituted by a metal film through which a light
current passes. This current may come from a backup secondary
battery constantly powered by the cell.
[0033] The cell is to advantage constituted by a group of basic
cell elements. The semiconductor medium is worked from a standard
wafer according to the geometry required. It is oxidised and made
porous in the relevant areas, so as to obtain the mechanical,
thermal and electrical functionalities necessary for the cell to
operate. The number in the group of basic cell elements is adapted
to the power requirements. It may then be encapsulated in the
exchanger-distributors described above.
[0034] The electrolytic membrane composed of a semiconductor medium
impregnated with an electrolytic polymer may be integrated into a
bipolar or unipolar architecture.
[0035] The cell according to the invention is particularly adapted
to powering low-consumption portable electronic devices called
nomads.
[0036] In preferred embodiments for the porous membrane, silicon is
made porous by electrochemical anodisation. The membrane shows an
important specific surface with a high surface roughness. The
exchange surface is therefore much higher than the area of the
membrane. In the method used to make the porous membrane, silicon
is coated by a native silicon dioxide layer, which is electrically
insulating. Therefore, the thickness of the membrane can be less
than the usual 100 .mu.m thick membrane. The thickness of the
membrane can therefore be around 40 .mu.m for example. The only
limit to the thickness is the mechanical stiffness of the
membrane.
[0037] The diameter of the channels and the porosity of the
membrane are defined by the conditions of anodisation and can be
chosen as wanted.
[0038] In some preferred embodiments, the transfer of the protons
is obtained thanks to the proton conductivity of molecules which
are bonded to the surface of the channels by covalent bonding. The
molecules suitable for such bonding are molecules that have an acid
group or a sulphonate group. They are bonded on all the surface of
the porous silicon.
[0039] In some preferred embodiments, the impregnation by
capillarity of polymers or monomers that can be polymerised
afterwards is however still possible, of course. The used polymers
can conduct protons, like perfluorosulphonate polymers (as Nafion
117.RTM., Flemion.RTM. or Aciplex.RTM.) or other materials, such as
for example siloxanes, sulphones, etherketone sulphonated
polymers.
[0040] The electrodes that can also act as catalysts are made by
spraying of a really thin layer of platinum on the rough surfaces
of the membrane.
a. BRIEF DESCRIPTION OF THE DRAWING.
[0041] The invention is illustrated by the following figures
without being restricted thereto.
[0042] FIG. 1 is a diagrammatic view showing a mobile telephone
with a built-in cell according to one possible embodiment of the
invention.
[0043] FIG. 2 is an exploded perspective view of the cell shown in
FIG. 1.
[0044] FIG. 3a is a diagrammatic view of the cell in
cross-section.
[0045] FIG. 3b is a cross-section view along the line AA in FIG.
3a.
[0046] FIG. 3c is a view from above of the cell in FIG. 3a.
[0047] FIGS. 4a and 4b are enlarged views of the transverse
cross-section of a cell according to the invention, at the level of
the electrolytic membrane.
[0048] FIG. 5a is a view from below of the air/cathode distribution
system.
[0049] FIG. 5b is a view from above of the fuel anode distribution
system.
[0050] FIG. 6 is a perspective view of the assembled cell.
[0051] FIG. 7 is a schematic longitudinal view of a membrane having
channels of different diameters.
[0052] FIG. 8 is a schematic bloc diagram showing the steps of a
method for making a preferred porous silicon membrane according to
a first embodiment.
[0053] FIG. 9 is a schematic representation of the steps of a
method for making a porous silicon membrane according to FIG.
8.
[0054] FIG. 10 is a schematic longitudinal view of the steps for
the filling of the channels of the first preferred embodiment of
the invention.
[0055] FIG. 11 is a schematic bloc diagram showing the steps of a
method for making a preferred porous silicon membrane according to
a second embodiment.
[0056] FIG. 12 is a schematic representation of the steps of a
method for making a porous silicon membrane according to FIG.
11.
[0057] FIG. 13 is a schematic longitudinal view of the steps for
the filling of the channels of the second preferred embodiment of
the invention.
[0058] FIG. 14 is a schematic longitudinal view of a third
preferred embodiment for a membrane according to the invention.
a. DETAILED DESCRIPTION OF THE INVENTION.
[0059] The cell--given the reference 1--shown in the figures
presents a planar architecture and is constituted by an assembly
which comprises a membrane and electrodes complex 3c and two
elements 3a, 3b forming exchangers/distributors between which said
complex 3c is encapsulated.
[0060] This cell 1 may be--as FIG. 1 shows--a cell integrated in
the housing B of a portable telephone. By way of example, it may be
able to achieve a 2 volt feed with a power of 2 Watts.
[0061] As is shown more exactly in FIGS. 2, 3a to 3c, as well as 4a
and 4b the complex 3c is constituted by an anode 8a and a cathode
8b between which a membrane 4 is interposed.
[0062] The membrane 4 and the metallised parts 8a, 8b which define
the anode 8a and the cathode 8b have, on one side and on the other
of the complex 3c, a plurality of recesses which define on the
membrane 4 a plurality of cell elements 5 for electrochemical
exchanges.
[0063] The membrane 4 is constituted by a wafer of an oxidised
semiconductor material (oxidised silicon for example), which has
been made porous in the areas corresponding to the cell elements 5.
This porosity is directed so as to obtain channels which are
parallel to each other.
[0064] To this end, this membrane 4 is previously processed using
masking and etching techniques known conventionally per se in
respect of semiconductor materials, so as to obtain in it the
recesses corresponding to the cell elements 5, and in the areas
corresponding to these cell elements 5, a plurality of
micro-channels 11 which pass through the membrane 4 and make it
porous, metallised parts corresponding to the electrodes 8a and 8b
being then deposited on one side and on the other respectively of
the membrane 4.
[0065] In the example shown in FIG. 4a, the porous semiconductor
impregnated with electrolytic polymer is coated with a layer
constituted by an electrode-catalyst complex 10.
[0066] As an alternative, as shown in FIG. 4b, the membrane 4 is
constituted at the level of the cell elements 5 by a complex of
basic membranes 12 separated by metal layers 13, the whole being
passed through by micro-channels 11 which ensure the passage of the
protons.
[0067] By referring to FIGS. 2 and 3a to 3c, and FIGS. 5a, 5b it
may be understood that the cell elements 5 of the membrane 4 are,
at the level of the anode 8a, supplied with fuel through diffusion
channels 6a which are provided in the component 3a and which lead
the fuel stored in a cartridge 2 to the cell elements 5.
[0068] This cartridge 2 is for example cylindrical in shape. It is
received in a receptacle provided for this purpose on the
exchanger/distributor component 3a.
[0069] At the level of the cathode 8b, the cell element 5 of the
membrane are supplied with air through diffusion channels 6b which
extend through the component 3b and emerge on the one hand in the
cell elements 5 and on the other hand outside the component 3b.
[0070] The fuel is particularly a methanol/water mixture. The
released protons diffuse in the membrane 4 of the basic cell
elements 5, whereas the electrons move to the cathode 8b.
[0071] CO.sub.2, water and water vapour are released at each cell
element 5.
[0072] The released CO.sub.2 is evacuated in the exchanger 3a. The
water formed at the cathode 8b may be evacuated by evaporation at
the exchangers 15 provided for this purpose in the component 3b. In
the component 3a, it may be recycled in the distribution system 6,
a micro-pump 9 being used to this end to pump this water helped by
the kinetics of the water vapour resulting from the exothermic
oxidation reaction.
[0073] The vertical position of use of the electronic
appliance--shown by the arrows in the figures--favours collection
in the lower part of the cell elements thus minimising the negative
impact of insulation from the presence of water on the active
surface of the cell element.
[0074] As may be seen more particularly in FIG. 3b, as well as in
FIGS. 5a, 5b and 6, metal lugs 16a, 16b are provided on the
component 3b forming the exchanger/distributor, which extend
through said component 3b and provide the connection of the anode
8a and of the cathode 8b to a printed circuit board 17 which is for
example a board which manages the power supply of the mobile
telephone B.
[0075] Preferentially electrodes are of a highly conductive
metal.
[0076] In all the following specification, the used abbreviations
are as follows.
[0077] ATES: allyltriethoxysilane
[0078] BTES: benzyltriethoxysilane
[0079] ClTMS: chlorotrimethylsilane
[0080] OTMS: 7-octenyltriethoxysilane
[0081] PTES: phenyltriethoxysilane
[0082] TEOS tetraethoxysilane
[0083] As described above and shown in FIG. 4a, the membrane used
in the cell according to the invention can be a porous silicon
membrane 4 impregnated with a proton conductive polymer in the
channels 11.
[0084] The polymer that is impregnated by capillarity in the
channels 11 is already under the form of long chemical chains
before getting into the channels 11. Therefore, the polymer has to
be diluted in a solvent to be able to enter the channels 11 and
form the conductive material.
[0085] Several possibilities can be chosen for the polymer to be
impregnated in the porous membrane.
[0086] The filling of the porosity of silicon by perfluorinated
polyelectrolytes with a sulfonic functional group such as
Nafion.RTM. 117, Aciplex analogs or Dow, or with a carboxylic
functional group such as Flemion is possible. Solutions of 5 to 20
mass-% by weight in water/alcohol solvents are introduced in
several steps. After passage of the solution, the porous material
is heated to eliminate the alcohols. As a result, subsequent
passages do not remove the polymer already introduced at previous
filling operations. See example 1 and 2.
EXAMPLE 1
[0087] Silicon microporous material is impregnated with Nafion.RTM.
117. One 10 .mu.L drop of Nafion.RTM. perfluorinated ion-exchange
resin at 5 wt % solution in a mixture of lower aliphatic alcohols
and water is placed on the silicon microporous material so that it
wets the inside space of the microporous material by capillary
action. Drying is done under controlled atmosphere at 20.degree. C.
and 90% relative humidity. This procedure is repeated on the other
surface. The microporous material is then treated with hot 3
mol.L.sup.-1 nitric acid over a period of 2 hours then washed in
distilled water over a period of two days by means of a Soxhlet. At
25.degree. C. and under 90% relative humidity, a conductivity of 30
mS/cm is obtained.
EXAMPLE 2
[0088] Silicon microporous material is impregnated with Nafion.RTM.
117. One 10 .mu.L drop of Nafion.RTM. perfluorinated ion-exchange
resin at 20 wt % solution in a mixture of lower aliphatic alcohols
and water is placed on the silicon microporous material so that it
wets the inside space of the microporous material by capillary
action. Drying is done under controlled atmosphere at 20.degree. C.
and 90% relative humidity. The microporous material is then placed
in hot 3 mol.L.sup.-1 nitric acid over a period of 2 hours then
washed in distilled water over a period of two days by means of a
Soxhlet.
[0089] The filling of the porosity with a polyelectrolyte having an
aromatic main chain such as polysulfones, polyether sulfones,
polyether-ether-ketone, polyphenylene oxide, polyphenylene sulfide,
ionic group carriers, sulfonic, phosphonic, carboxylic is also
possible. The polyelectrolytes can comprise only one of these
functional groups or can combine a plurality of these functional
groups, e.g. phosphonic/sulfonic, sulfonic/carboxlic,
sulfonic/phosphonic/carboxlic. See example 3.
EXAMPLE 3
[0090] 2 g of Udel 3500 @ polysulfone are dissolved in 20 ml of
dichloroethane. Trimethylsilylchlorosulfonate is added so as to
obtain an exchange capacity of 1.8 moles of protons/kg. After
precipitation in ethanol, the polyelectrolyte is dissolved in a 4/1
mixture of dichloroethane and isopropanol. Solutions of sulfonated
polysulfones are introduced into the porosity of the silicon by
capillary action using one 10 .mu.L drop on the surface of the
microporous material. The polysulfones used have a sulfonation rate
of 1.6 to 1.9 protons per kilogram. After introduction of the
polysulfone, conductivities varying between 20 and 70 mS/cm were
obtained depending on the sulfonation rate.
[0091] The sulphonation can also be done after the introduction of
the polymer in the channels. The filling of the porosity can be
done on the basis of a polymer having an aromatic main chain such
as polysulfone, polyether sulfone, polyether-ether-ketone,
polyphenylene oxide, polyphenylene sulfide. After filling of the
porosity using the polymer solution, the reagent enabling
introduction of the ionic group is introduced into the porosities.
The reaction thus takes place in the porosity.
[0092] It is time consuming to let the polymer impregnate in the
channels 11. Furthermore, the channels 11 have to be large enough
to allow the long chemical chains to enter the channels 11. The
fact that the channels are of large diameter can provoke leaks of
the fuel and/or the oxidant through the membrane.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0093] In the preferred embodiments for the silicon porous
membrane, the diameter of the channels is reduced, which allows
greater tightness with respect to the fuel and/or the oxidant.
[0094] Several methods are possible to make the membranes of the
preferred embodiments.
[0095] In all those methods, the first step is the use of a wafer
of doped and oxidized silicon. The thickness of the wafer is for
example equal to 500 .mu.m. The second step is the making of square
membranes of, for instance, 40 .mu.m in thickness and 3 mm on each
side. Of course, the given dimensions are just examples and can be
changed depending on the use of the membrane. The making of the
thinner membranes out of the wafer is conducted by lithography and
chemical etching.
[0096] The current collectors for the method are made as soon as
this second step by a coating of gold on the oxide layer of the
silicon wafer. The collectors are masks for the subsequent step
which is the making of the porous silicon by anodisation in a
solution. The solution is for example a solution of hydrofluoric
acid/water/ethanol. The chemical composition of the solution, the
current density of anodisation, the nature and the concentration of
the silicon doping agent are important parameters to define the
size of the channels and the final porosity.
[0097] The beginning of the drilling of the membrane is monitored
by a decrease in the tension between the terminals of the anodizer.
As the thickness of the membrane is not rigorously the same all
over the surface, and as the method of anodisation is not perfectly
homogeneous, it is practically impossible to pierce all the
channels at the same time.
[0098] From that moment, it is not necessary to go on with
anodisation, for the majority of the current goes through the
opened channels.
[0099] Another technique must be employed to etch the rear surface
of the membrane and allow the piercing of all the channels. The
said other technique is the plasma reactive etching. It gets rid of
the few extra microns to open the channel and increases the
roughness of the surface.
[0100] Then a proton conductive material is introduced in the
channels that have been drilled. The material and the technique
used are described in more details further down in the
specification.
[0101] In all the methods used to obtain preferred embodiments, and
as it is shown in FIG. 4a, the last step is the coating of the
surfaces of the membrane 4 by a catalyst 10. At that stage, all the
channels 11 are already filled with conductive material.
[0102] A thin layer 10 of platinum is coated by cathodic spraying
on the two surfaces of the silicon porous membrane 4. This layer 10
must however be thick enough to allow the conduction of the
electrons till the current collector. The coating is made so as to
be above the threshold of percolation.
[0103] It is also possible to structure the porous medium that is
shaped through its thickness. For example, as it is shown in FIG.
7, it is possible to make channels 71 having a small diameter at
the centre of the membrane 70 and channels having a larger diameter
on the outer surface of the membrane 70. The large diameters are
better adapted to the catalyst 73.
[0104] First Preferred Embodiment.
[0105] Here is described an example of a method to obtain a
membrane according to the first preferred embodiment.
[0106] The first example of preferred embodiment described here is
a silicon porous membrane made by intrinsic anodisation. The porous
membrane is obtained by anodisation. The membrane is impregnated by
a monomer of Nafion 117.RTM. as will be explained further in the
specification.
[0107] The different steps of the method are as follows, and are
shown in FIG. 8 and FIG. 9.
[0108] In the first step 81 of FIG. 8, shown as well in FIG. 9(a),
an N-type blank wafer 90 of silicon is prepared. The wafer 90 is
<100> oriented, and the resistivity of the wafer 90 is from
0.3 to 1 _.cm for example.
[0109] In step 82, the wafer 90 is oxidized by a thermal oxidizing,
in an oven, at a temperature of 1000.degree. C. for instance. A
flux of oxygen and water vapour flows in the oven. The resulting
layer of silicon oxide is referred to as 91 in FIG. 9(b).
[0110] In step 83, shown in FIG. 9(c), a layer 92 of chromium is
coated on each surface of the wafer. The coating is conducted by
cathodic spraying. The layer 92 has for example a thickness of 150
nm. This layer 92 serves as a layer of hanging-up for a layer 93 of
gold. The layer of gold is for instance 1 .mu.m-thick. The coating
of the gold layer 93 is made thanks to a cathodic spraying as
well.
[0111] In step 84, a photolithography is realised on the wafer 90
which has been metallized in step 83. The photolithography is
realised on each of the surface thanks to a chromed glass mask. A
photosensitive resin 94 is firstly coated on the wafer 90, above
the gold layer 93, as shown in FIG. 9(d). The patterns of the mask
are then reproduced by exposure of the resin 94 to ultraviolet
radiation. The exposed parts of the resin 94 are then removed in an
adapted solvent. The metal layer 93 is therefore bare on the
desired locations for the membranes.
[0112] In step 85, the bare patterns are then etched by adapted
etching solutions. The layers of gold 93, chromium 92 and silicon
dioxide 91 are therefore etched. The result of such etchings is
shown in FIG. 9(e). The etching of the silicon dioxide 91 is done
in an ammonium bifluoride (BHF) solution (7 vol. NH.sub.4F 40%+1
vol HF 50%). The etching of the silicon membrane 90 is done is a
KOH solution, with a concentration of 41%. A 40 .mu.m-thick
membrane 95 is obtained and the result of such an etching is shown
in FIG. 9(f). The resin is also removed at that stage.
[0113] In step 86, the drilling of the membrane 95 is done so as to
make the membrane 95 porous. The drilling is made by anodisation
without current thanks to the potential difference between the
remaining gold layer 93 and the silicon in a bath composed of
HF:ethanol:water:hydrogen dioxide. The proportions of each
component can be, for instance, 9:4:11:1. The result of the
drilling is the channels 96 which are shown in FIG. 9(g).
[0114] In a step 87, the channels 96 are then made hydrophilic
thanks to two successive treatments. The membrane 95 is firstly put
in a solution containing 80% of sulphuric acid and 20% of hydrogen
peroxide. The membrane stays in the solution during around 60
minutes. Secondly, the membrane is put in a container where each
surface is exposed to ultraviolet rays and an ozone flux. The
exposure of each surface lasts around 10 minutes.
[0115] In step 88, the channels 96 are impregnated by capillarity
with 10 .mu.l of a 5% solution of Nafion 117 .RTM.. This kind of
solution can be encountered under the Fluka brand.
[0116] As explained above, to advantage, the solution contains a
monomer instead of a polymer.
[0117] FIG. 10 illustrates the steps of such a method. A membrane
100 has channels, referred to as 101, 102 and 103 for example,
which are obtained for example by the anodisation technique
described above.
[0118] According to this method, the material that is the proton
conductive material is entered in the channels 101, 102 and 103
under the form of a monomer or oligomer 104.
[0119] The three channels 101, 102 and 103 schematically refer to
different steps of transformation of the proton conductive material
of the first preferred embodiment. In the channel 101, the monomer
104 is introduced in the channels. The introduction can be done by
impregnation by capillarity for instance. The channel 102
represents schematically the step when the monomer starts to get
cross-linked in the channels. This cross-linking of the monomer is
made by the use of heat and/or catalysts. The channel 103
represents the last step of the transformation of the proton
conductive material. In this last step, the material is now under
the form of a polymer 106 due to cross-linking. The polymer 106 is
now in the solid state and blocks the channels 101, 102, 103. The
protons are conducted by the polymer 106 through the membrane 100.
The membrane 100 is tight to the fuel and/or the fuel oxidizer.
[0120] Therefore, the membrane 100 obtained by this method is the
same as the embodiment shown in FIG. 4a. However, the diameter of
the channels 101, 102 and 103 can be reduced, since the material is
introduced in the channel as a monomer. The impregnation is quicker
as well. The typical size of the channels is under 100 nm and can
be of the order of magnitude of 25-30 nm in some applications.
[0121] Referring again to FIG. 8, in step 89, a thin layer of
platinum is coated by cathodic spraying on each surface of the
membrane to get an electrode 10 as shown in FIG. 4a. The thickness
of the layer is equal to 1 to 2 nm. Each layer is therefore an
electrode and a catalyst.
[0122] The monomer or oligomer 104 introduced in the channel 101
can be a pure monomer or a co-monomer. In the latter case, the
polymer 106 obtained will be a copolymer. Here is listed a number
of different examples for the monomer or oligomer.
[0123] First, the filling of the porosities of silicon by oligomers
having a polysiloxane main chain bearing sulfonic functions, in the
form of acid or alkali, in concentrated solution or in molten form,
in the presence of an initiator enabling post-polymerization after
filling the porosity is possible. The cross-linking can be induced
by heating above the temperature of decomposition of the initiator,
or by UV irradiation, electron bombardment, etc. See examples 4 to
18.
EXAMPLE 4
[0124] Different proportions were used for obtaining copolymers of
BTES/ATES: 5, 10 and 15 mole % of ATES, using 10.sup.-2 mole of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. The precipitate is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. Polycondensation is
continued for 48 hours at 60.degree. C. The copolymer is
re-dissolved in dichloromethane and the residual silanol functional
groups are blocked by the addition of 10.sup.-3 moles of ClTMS. The
copolymers obtained are characterized, in solution in
tetrahydrofurane, by SEC (size exclusion chromatography) over a set
of ultrastyragel columns having a porosity 500, 10.sup.3 and
10.sup.4 .ANG., the masses being evaluated in polystyrene
equivalent, as shown in Table 1.
1 TABLE 1 Samples BTES/ATES (10%) BTES/ATES (15%) M.sub.w 1900 3040
M.sub.n 1500 2100 I 1.26 1.45 M.sub.w: average molecular weight in
weight M.sub.n: average molecular weight in number I: polydisperity
index
[0125] After purification and drying (48 hours at 60.degree. C.),
the copolymer is re-dissolved in dichloroethane in a glove box
under argon. Sulfonation of the copolymer is done in a glove box
over a period of 12 hours under agitation and at room temperature,
by the addition drop-wise of trimethylsilylchlorosulfonate (TMSCS)
in the proportion of 2 moles of TMSCS per kilogram of copolymer.
The trimethylsilyl sulfonate groups are hydrolyzed to sulfonic
groups either by contact with atmospheric humidity over the period
of 48 hours or by treatment with ethanol. Once purified, a 50 mass
% of sulfonated copolymer in dichloroethane is introduced by
capillary action into the microporous silicon, one drop being 10
.mu.L. This solution contains 1 mole of dibenzoyl peroxide to 4
moles of double bonds for cross-linking the copolymer by the
thermally initiated radical route. Cross-linking is done under
argon at 85.degree. C. over a period of 12 hours. The system
obtained in this fashion is washed in distilled water over 12
hours.
EXAMPLE 5
[0126] Different proportions were used for obtaining copolymers of
BTES/ATES: 5, 10 and 15 mole % of ATES using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
is dried and polycondensation done over a period of 48 hours at
60.degree. C. The copolymer is re-dissolved in dichloromethane and
the uncondensed hydroxyls are fixed by the addition of 10.sup.-3
moles of ClTMS. After purification and drying (48 hours at
60.degree. C.), the copolymer is re-dissolved in dichloroethane in
the glove box (inert atmosphere/argon). Sulfonation of the
copolymer is done using trimethylsilylchorosulfonate, 2 moles per
kilogram of copolymer in the glove box over a period of 12 hours
under agitation and at room temperature. The trimethylsilyl
sulfonate groups are hydrolyzed to sulfonates in air over a period
of 48 hours. Once purified, a 50 mass % of sulfonated copolymer in
dichloroethane is introduced by capillary action into the
microporous silicon, one drop being 10 .mu.L. This solution
contains 1 mole of dibenzoyl peroxide to 4 moles of double bonds
for cross-linking by the thermally initiated radical route and one
mole of 1,7-octadiene to two moles of ATES. Cross-linking is done
under argon at 85.degree. C. over a period of 12 hours. The system
obtained in this fashion is washed in distilled water over a period
of 12 hours.
EXAMPLE 6
[0127] Different proportions were used for obtaining BTES/ATES
copolymers: 5, 10 and 15 mole % of ATES using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
is dried and polycondensation done over a period of 48 hours at
60.degree. C. The copolymer is re-dissolved in dichloromethane and
the uncondensed hydroxyls are fixed by the addition of 10.sup.-3
moles of ClTMS. The copolymers obtained are characterized by dry
size exclusion chromatography (SEC) in tetrahydrofurane, the masses
being evaluated in styrene equivalent. After purification and
drying (48 hours at 60.degree. C.), the copolymer is re-dissolved
in dichloroethane in the glove box (inert atmosphere/argon).
Sulfonation of the copolymer is done using
trimethylsilylchorosulfonate, 2 moles per kilogram of copolymer in
the glove box over a period of 12 hours under agitation and at room
temperature. The trimethylsilyl sulfonate groups are hydrolyzed to
sulfonates in air over a period of 48 hours. Once purified, a 50
mass % of sulfonated copolymer in dichloroethane is introduced by
capillary action into the microporous silicon, one drop being 10
.mu.L. This solution contains 10.sup.-3 moles of Irgacure.RTM. 1959
(CIBA), a photoinitiator having its extinction zone around 275 nm.
The copolymer is thus cross-linked by radical photoinitiation.
Cross-linking is done under UV and argon over a period of 10
minutes after having evaporated the major part of the solvent. The
system is then placed for 2 days in an oven at 75.degree. C. The
system obtained in this fashion is washed in distilled water over
12 hours.
EXAMPLE 7
[0128] Different proportions were used for obtaining copolymers of
BTES/ATES: 5, 10 and 15 mole % of ATES using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
is dried and polycondensation done over a period of 48 hours at
60.degree. C. The copolymer is re-dissolved in dichloromethane and
the uncondensed hydroxyls are fixed by the addition of 10.sup.-3
moles of ClTMS. Once purified, the product is dried at 100.degree.
C. under vacuum. The copolymer obtained in this fashion is
re-dissolved in the glove box under argon in dichloromethane in
order to obtain a 50 mass % solution. This solution contains
10.sup.-3 moles of Irgacure.RTM. 1959 (CIBA), a photoinitiator
having its extinction zone around 275 nm. The copolymer is thus
cross-linked by the photochemically initiated radical route.
Cross-linking is done under UV and argon over a period of 10
minutes after having allowed a large portion of the solvent to
escape after the introduction of 10 .mu.L of solution into the
microporous silicon material by capillary action. The system
obtained is sulfonated with chlorosulfonic acid, 2 moles per
kilogram of copolymer with a 10 mole % excess, in the glove box
over a period of 12 hours without agitation, at room temperature.
The system obtained in this fashion is washed in distilled water
over a period of 12 hours.
EXAMPLE 8
[0129] Different proportions were used for obtaining copolymers of
BTES/OTMS: 5, 10 and 15 mole % of OTMS using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
is dried and polycondensation is done over 48 hours at 60.degree.
C. The copolymer is re-dissolved in dichloromethane and the
uncondensed hydroxyls are fixed by the addition of 10.sup.-3 moles
of ClTMS. The copolymers obtained are characterized by size
exclusion chromatography (SEC) in tetrahydrofurane, the masses
being evaluated in styrene equivalent, as shown in Table 2.
2 TABLE 2 Samples BTES/OTMS (10%) BTES/OTMS (15%) Mw 4300 5760 Mn
2520 3140 I 1.70 1.84
[0130] After purification and drying (48 hours at 60.degree. C.),
the copolymer is re-dissolved in dichloroethane in the glove box
(inert atmosphere/argon). Sulfonation of the copolymer is done
using trimethylsilylchorosulfonate, 2 moles per kilogram of
copolymer in the glove box over a period of 12 hours under
agitation and at room temperature. The trimethylsilyl sulfonate
groups are hydrolyzed to sulfonates in air over a period of 48
hours. By modulated DSC, the vitreous transition temperature (with
the initial copolymer in 15% of OTMS) at 2.degree. C. min.sup.-1
with variations of amplitude of .+-.1.degree. C. min.sup.-1 and of
period of 60 seconds, by assuming the valley of the transition to
be 258 K. Once purified, a 50 mass % of sulfonated copolymer in
dichloroethane is introduced by capillary action into the
microporous silicon, one drop being 10 .mu.L. This solution
contains 1 mole of dibenzoyl peroxide to 4 moles of double bonds
for cross-linking the copolymer by the thermally initiated radical
route. Cross-linking is done under argon at 85.degree. C. over a
period of 12 hours. The system obtained in this fashion is washed
in distilled water over 12 hours.
EXAMPLE 9
[0131] Different proportions were used for obtaining copolymers of
BTES/OTMS: 5, 10 and 15 mole % of OTMS using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
is dried and polycondensation done over a period of 48 hours at
60.degree. C. The copolymer is re-dissolved in dichloromethane and
the uncondensed hydroxyls are fixed by the addition of 10.sup.-3
moles of ClTMS. After purification and drying (48 hours at
60.degree. C.), the copolymer is re-dissolved in dichloroethane in
the glove box (inert atmosphere/argon). Sulfonation of the
copolymer is done using trimethylsilylchorosulfonate, 2 moles per
kilogram of copolymer in the glove box over a period of 12 hours
under agitation and at room temperature. The
trimethylsilylsulfonate groups are hydrolyzed to sulfonates in air
over a period of 48 hours. Once purified, a 50 mass % of sulfonated
copolymer in dichloroethane is introduced by capillary action into
the microporous silicon, one drop being 10 .mu.L. This solution
contains 1 mole of dibenzoyl peroxide to 4 moles of double bonds
and one mole of 1,7-octadiene to two moles of OTMS is added for
cross-linking by the thermally initiated radical route.
Cross-linking is done under argon at 85.degree. C. over a period of
12 hours. The system obtained in this fashion is washed in
distilled water over 12 hours.
EXAMPLE 10
[0132] Different proportions were used for obtaining copolymers of
BTES/OTMS 5, 10 and 15 mole % of OTMS using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
is dried and polycondensation done over a period of 48 hours at
60.degree. C. The copolymer is re-dissolved in dichloromethane and
the uncondensed hydroxyls are fixed by the addition of 10.sup.-3
moles of ClTMS. After purification and drying (48 hours at
60.degree. C.), the copolymer is re-dissolved in dichloroethane in
the glove box (inert atmosphere/argon). Sulfonation of the
copolymer is done using trimethylsilylchorosulfonate, 2 moles per
kilogram of copolymer in the glove box over a period of 12 hours
under agitation and at room temperature. The trimethylsilyl
sulfonate groups are hydrolyzed to sulfonates in air over a period
of 48 hours. Once purified, a 50 mass % of sulfonated copolymer in
dichloroethane is introduced by capillary action into the
microporous silicon, one drop being 10 .mu.L. This solution
contains 10.sup.-3 moles of Irgacure.RTM. 1959 (CIBA), a
photoinitiator having its extinction zone around 275 nm. The
copolymer is thus cross-linked by the photochemically initiated
radical route. Cross-linking is done under UV and argon over a
period of 10 minutes after having allowed the major part of the
solvent to escape. The system is then placed for 2 days in an oven
at 75.degree. C. The system thus obtained is washed in distilled
water for 12 hours.
EXAMPLE 11
[0133] Different proportions were used for obtaining copolymers of
BTES/ATES: 5, 10 and 15 mole % of OTMS using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
is dried and polycondensation done over a period of 48 hours at
60.degree. C. The copolymer is re-dissolved in dichloromethane and
the uncondensed hydroxyls are fixed by the addition of 10.sup.-3
moles of ClTMS. After purification and drying (48 hours at
60.degree. C.), the copolymer is re-dissolved in dichloroethane in
the glove box (inert atmosphere/argon). Sulfonation of the
copolymer is done using trimethylsilylchorosulfonate, 2 moles per
kilogram of copolymer in the glove box over a period of 12 hours
under agitation and at room temperature. The trimethylsilyl
sulfonate groups are hydrolyzed to sulfonates in air over a period
of 48 hours. Once purified, a 50 mass % of sulfonated copolymer in
dichloroethane is introduced by capillary action into the
microporous silicon, one drop being 10 .mu.L. This solution
contains 10.sup.-3 moles of Irgacure.RTM. 1959 (CIBA), a
photoinitiator having its extinction zone around 275 nm and one
mole of 1,7-octadiene to two moles of OTMS. The copolymer is thus
cross-linked by the photochemically initiated radical route.
Cross-linking is done under UV and argon over a period of 10
minutes after having allowed the major part of the solvent to
escape. The system is then placed for 2 days in an oven at
75.degree. C. The system thus obtained is washed in distilled water
for 12 hours.
EXAMPLE 12
[0134] The same protocol as in Example 4 is used by replacing the
BTES with PTES.
EXAMPLE 13
[0135] The same protocol as in Example 5 is used by replacing the
BTES with PTES.
EXAMPLE 14
[0136] The same protocol as in Example 7 is used by replacing the
BTES with PTES.
EXAMPLE 15
[0137] The same protocol as in Example 8 is used by replacing the
BTES with PTES.
EXAMPLE 16
[0138] The same protocol as in Example 9 is used by replacing the
BTES with PTES.
EXAMPLE 17
[0139] The same protocol as in Example 10 is used by replacing the
BTES with PTES.
EXAMPLE 18
[0140] The same protocol as in Example 11 is used by replacing the
BTES with PTES.
[0141] Of course, there are other possibilities. The same protocol
as in Example 6 is used by replacing the BTES with PTES for
example.
[0142] In examples 4 to 18, the sulphonation is done before the
monomer or oligomer is introduced in the channels or porosity. The
sulphonation can be done after the filling of the channels or
porosity.
[0143] In the following example, the filling of the porosity of the
silicon is done using oligomers having a polysiloxane main chain,
in concentrated solution or in the molten state, in the presence of
an initiator enabling post-polymerization after filling of the
porosity. After thermal or photochemical cross-linking the reagent
enabling introduction of the ionic group is introduced into the
porosity. The reaction thus takes place in the porosity. See
examples 19 to 38.
EXAMPLE 19
[0144] Different proportions were used for obtaining copolymers of
BTES/ATES: 5, 10 and 15 mole % of ATES using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
in this fashion is dried and polycondensation done over 48 hours at
60.degree. C. The copolymer is re-dissolved in dichloromethane and
the uncondensed hydroxyls are fixed by the addition of 10.sup.-3
moles of ClTMS. Once purified, the product is dried at 100.degree.
C. under vacuum. The copolymer obtained in this fashion is
re-dissolved in the glove box under argon in dichloromethane in
order to obtain a 50 mass-% solution. This solution contains 1 mole
of dibenzoyl peroxide to 4 moles of double bonds for cross-linking
the copolymer by thermally initiated radical means. Cross-linking
is done under argon at 85.degree. C. over a period of 12 hours
after introduction of 10 .mu.L of solution by capillary action into
silicon microporosities. The system obtained is sulfonated with
chlorosulfonic acid, 2 moles per kilogram of copolymer with a 10
mole % excess, in the glove box over a period of 12 hours at room
temperature. The system obtained in this fashion is washed in
distilled water over 12 hours. The system obtained using copolymer
with 10 mole % ATES has a conductivity of 2*10.sup.-2
S.cm.sup.-1.
EXAMPLE 20
[0145] Different proportions were used for obtaining copolymers of
BTES/OTMS: 5, 10 and 15 mole % of OTMS using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
is dried and polycondensation done over a period of 48 hours at
60.degree. C. The copolymer is re-dissolved in dichloromethane and
the uncondensed hydroxyls are fixed by the addition of 10.sup.-3
moles of ClTMS. Once purified, the product is dried at 100.degree.
C. under vacuum. The copolymer obtained in this fashion is
re-dissolved in the glove box under argon in dichloromethane in
order to obtain a 50 mass-% solution. This solution contains 1 mole
of dibenzoyl peroxide to 4 moles of double bonds for cross-linking
the copolymer by the thermally initiated radical route.
Cross-linking is done under argon at 85.degree. C. over a period of
12 hours after introduction of 10 .mu.L of solution by capillary
action into the silicon microporosities. The system obtained is
sulfonated with chlorosulfonic acid, 2 moles per kilogram of
copolymer with a 10 mole % excess, in the glove box over a period
of 12 hours at room temperature. The system obtained in this
fashion is washed in distilled water over 12 hours.
EXAMPLE 21
[0146] Different proportions were used for obtaining copolymers of
BTES/ATES: 5, 10 and 15 mole % of ATES using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
is dried and polycondensation done over a period of 48 hours at
60.degree. C. The copolymer is re-dissolved in dichloromethane and
the uncondensed hydroxyls are fixed by the addition of 10.sup.-3
moles of ClTMS. Once purified, the product is dried at 100.degree.
C. under vacuum. The copolymer obtained in this fashion is
re-dissolved in the glove box under argon in dichloromethane in
order to obtain a 50 mass % solution. This solution contains
10.sup.-3 moles of Irgacure.RTM. 1959 (CIBA), a photoinitiator
having its extinction zone around 275 nm. The copolymer is thus
cross-linked by the photochemically initiated radical route.
Cross-linking is done under UV and argon over a period of 10
minutes after having allowed a large portion of the solvent to
escape after the introduction of 10 .mu.L of solution into the
microporous silicon material by capillary action. The system
obtained is sulfonated with chlorosulfonic acid, 2 moles per
kilogram of copolymer with a 10 mole % excess, in the glove box
over a period of 12 hours without agitation, at room temperature.
The system obtained in this fashion is washed in distilled water
over a period of 12 hours.
EXAMPLE 22
[0147] Different proportions were used for obtaining copolymers of
BTES/OTMS: 5, 10 and 15 mole % of OTMS using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
is dried and polycondensation done over a period of 48 hours at
60.degree. C. The copolymer is re-dissolved in dichloromethane and
the uncondensed hydroxyls are fixed by the addition of 10.sup.-3
moles of ClTMS. Once purified, the product is dried at 100.degree.
C. under vacuum. The copolymer obtained in this fashion is
re-dissolved in the glove box under argon in dichloromethane in
order to obtain a 50 mass % solution. This solution contains
10.sup.-3 moles of Irgacure.RTM. 1959 (CIBA), a photoinitiator
having its extinction zone around 275 nm. The copolymer is thus
cross-linked by radical photoinitiation. Cross-linking is done
under UV and argon over a period of 10 minutes after having allowed
a large portion of the solvent to escape after the introduction of
10 .mu.L of solution into the microporous silicon material by
capillary action. The system obtained is sulfonated with
chlorosulfonic acid, 2 moles per kilogram of copolymer with a 10
mole % excess, in the glove box over a period of 12 hours without
agitation, at room temperature. The system obtained in this fashion
is washed in distilled water over a period of 12 hours.
EXAMPLE 23
[0148] Different proportions were used for obtaining copolymers of
BTES/ATES: 5, 10 and 15 mole % of ATES using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
is dried and polycondensation done over a period of 48 hours at
60.degree. C. The copolymer is re-dissolved in dichloromethane and
the uncondensed hydroxyls are fixed by the addition of 10.sup.-3
moles of ClTMS. Once purified, the product is dried at 100.degree.
C. under vacuum. The copolymer obtained in this fashion is
re-dissolved in the glove box under argon in dichloromethane in
order to obtain a 50 mass % solution. This solution contains 1 mole
of dibenzoyl peroxide to 4 moles of double bonds and one mole of
1,7-octadiene to two moles of ATES is added for cross-linking by
the thermally initiated radical route. Cross-linking is done under
argon at 85.degree. C. over a period of 12 hours after introduction
of 10 .mu.L of solution by capillary action into silicon
microporosities. By modulated DSC, the vitreous transition
temperature (with the initial copolymer in 10% ATES) at 2.degree.
C. min.sup.-1 with variations of amplitude of +1.degree. C.
min.sup.-1 and 60 seconds of period by assuming the valley of the
transition is 290 K. The system obtained is sulfonated with
chlorosulfonic acid, 2 moles per kilogram of copolymer with a 10
mole % excess, in the glove box over a period of 12 hours at room
temperature. The system obtained in this fashion is washed in
distilled water over 12 hours.
EXAMPLE 24
[0149] Different proportions were used for obtaining copolymers of
BTES/OTMS: 5, 10 and 15 mole % of OTMS using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
is dried and polycondensation done over a period of 48 hours at
60.degree. C. The copolymer is re-dissolved in dichloromethane and
the uncondensed hydroxyls are fixed by the addition of 10.sup.-3
moles of ClTMS. Once purified, the product is dried at 100.degree.
C. under vacuum. The copolymer obtained in this fashion is
re-dissolved in the glove box under argon in dichloromethane in
order to obtain a 50 mass % solution. This solution contains 1 mole
of dibenzoyl peroxide to 4 moles of OTMS and one mole of
1,7-octadiene to two moles of OTMS for cross-linking by the
thermally initiated radical route. Cross-linking is done under
argon at 85.degree. C. over a period of 12 hours after introduction
of 10 .mu.L of solution by capillary action into silicon
microporosities. The system obtained is sulfonated with
chlorosulfonic acid, 2 moles per kilogram of copolymer with a 10
mole % excess, in the glove box over a period of 12 hours at room
temperature. The system obtained in this fashion is washed in
distilled water over 12 hours.
EXAMPLE 25
[0150] Different proportions were used for obtaining copolymers of
BTES/ATES: 5, 10 and 15 mole % of ATES using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
is dried and polycondensation done over a period of 48 hours at
60.degree. C. The copolymer is re-dissolved in dichloromethane and
the uncondensed hydroxyls are fixed by the addition of 10.sup.-3
moles of ClTMS. Once purified, the product is dried at 100.degree.
C. under vacuum. The copolymer obtained in this fashion is
re-dissolved in the glove box under argon in dichloromethane in
order to obtain a 50 mass % solution. This solution contains
10.sup.-3 moles of Irgacure.RTM. 1959 (CIBA), a photoinitiator
having its extinction zone around 275 nm and one mole of
1,7-octadiene to two moles of ATES. The copolymer is thus
cross-linked by the photochemically initiated radical route.
Cross-linking is done under UV and argon over a period of 10
minutes after having allowed a large portion of the solvent to
escape after the introduction of 10 .mu.L of solution into the
microporous silicon material by capillary action. The system
obtained is sulfonated with chlorosulfonic acid, 2 moles per
kilogram of copolymer with a 10 mole % excess, in the glove box
over a period of 12 hours without agitation, at room temperature.
The system obtained in this fashion is washed in distilled water
over 12 hours.
EXAMPLE 26
[0151] Different proportions were used for obtaining copolymers of
BTES/OTMS: 5, 10 and 15 mole % of OTMS using 10.sup.-2 moles of
BTES. The synthesis starts by hydrolysis of half of the ethoxy
groups. The polycondensation that follows is catalyzed by the
fluoride (F.sup.-) ion. The NH.sub.4F solution is obtained by
dissolving 6 g of NH.sub.4F in 100 mL of methanol. After agitation
at room temperature for 3 hours, the excess NH.sub.4F is filtered.
The solution is maintained under agitation at room temperature for
48 hours, during which the polymer precipitates. This latter is
re-dissolved in dichloromethane and the solution is filtered in
order to remove the residual NH.sub.4F. The dichloromethane and the
methanol are removed by rotary evaporation. The copolymer obtained
is dried and polycondensation done over a period of 48 hours at
60.degree. C. The copolymer is re-dissolved in dichloromethane and
the uncondensed hydroxyls are fixed by the addition of 10.sup.-3
moles of ClTMS. Once purified, the product is dried at 100.degree.
C. under vacuum. The copolymer obtained in this fashion is
re-dissolved in the glove box under argon in dichloromethane in
order to obtain a 50 mass % solution. This solution contains
10.sup.-3 moles of Irgacure.RTM. 1959 (CIBA), a photoinitiator
having its extinction zone around 275 nm and one mole of
1,7-octadiene to two moles of OTMS. The copolymer is thus
cross-linked by the photochemically initiated radical route.
Cross-linking is done under UV and argon over a period of 10
minutes after having allowed a large portion of the solvent to
escape after the introduction of 10 .mu.L of solution into the
microporosity by capillary action. The system obtained is
sulfonated with chlorosulfonic acid, 2 moles per kilogram of
copolymer with a 10 mole % excess, in the glove box over a period
of 12 hours without agitation, at room temperature. The system
obtained in this fashion is washed in distilled water over 12
hours.
EXAMPLE 27
[0152] The same protocol as in Example 19 is used by replacing the
BTES with PTES.
EXAMPLE 28
[0153] The same protocol as in Example 20 is used by replacing the
BTES with PTES.
EXAMPLE 29
[0154] The same protocol as in Example 21 is used by replacing the
BTES with PTES.
EXAMPLE 30
[0155] The same protocol as in Example 22 is used by replacing the
BTES with PTES.
EXAMPLE 31
[0156] The same protocol as in Example 23 is used by replacing the
BTES with PTES.
EXAMPLE 32
[0157] The same protocol as in Example 24 is used by replacing the
BTES with PTES.
EXAMPLE 33
[0158] The same protocol as in Example 25 is used by replacing the
BTES with PTES.
EXAMPLE 34
[0159] The same protocol as in Example 26 is used by replacing the
BTES with PTES.
EXAMPLE 35
[0160] A series of samples of initial compositions in moles of
TEOS.sub.n-BTES.sub.(1-n) (with n=0.1, 0.4, 1) was synthesized
using as the catalyst NH.sub.4F after hydrolysis of half of the
ethoxy groups. After 48 hours of reaction at room temperature, the
supernatant solution was removed. The precipitate was collected in
dichloromethane. The 0 and 20% TEOS samples did not, with the
exception of NH.sub.4F, produce any product insoluble in
CH.sub.2Cl.sub.2 and there was 40% of insoluble product in the
dichloroethane for the 40% samples. For the 40% samples, the
insoluble fractions were washed in methanol and the same method was
used for pure TEOS.
[0161] Two 40% TEOS samples, one 10% TEOS sample and pure TEOS were
synthesized using the same catalyst. Two BTES/TEOS (60/40) samples
were done at the time of hydrolysis prior to their mixing. For
sample A, the two compounds were mixed immediately and for B,
hydrolysis continued for about 10 minutes. The results by SEC (size
exclusion chromatography) in tetrahydrofurane, the masses being in
styrene equivalent, are presented in the following table 3:
3TABLE 3 BTES/TEOS (90/10), BTES/TEOS (60/40) BTES/TEOS(60/40) Pure
Samples sulfonated (A) (B) TEOS Mw 1486 2889 15542 ** Mn 1261 2017
4458 ** I 1.18 1.43 3.49 ** (*: poly pure TEOS does not dissolve in
THF)
[0162] Thermal analysis by DSC shows that the vitreous transition
temperature of the polyTEOS is around 438 K.
[0163] After polycondensation over a period of 48 h at 60.degree.
C. in the oven, the BTES/TEOS (90/10) and BTES/TEOS (60/40) samples
were sulfonated by chlorosulfonic acid, which is introduced
typically in the stoichiometry of 20% relative to BTES in
dichloromethane. All of the products were immediately precipitated
in the solvent. The results of testing of satisfactory or
unsatisfactory solvents of sulfonated BTES/TEOS (90/10) are given
in the following table 4:
4 TABLE 4 Good Solvents Non-Solvents Ethyl alcohol Water 25.degree.
C. N,N-dimethylformamide dimethyl Dichloroethane acetal Methyl
sulfoxide Boiling distilled water
[0164] 40% sulfonated BTES/TEOS does not dissolve in water, ethyl
alcohol, dichloromethane, methyl alcohol and acetone. Concentrated
solutions of 10% sulfonated BTES/TEOS in the different good
solvents were introduced into the space of the microporous silicon
material by capillary action by depositing a 10 .mu.L drop. The
systems obtained in this fashion were left for one hour in the open
air, then washed in distilled water for a period of 12 hours. For
40% BTES/TEOS, copolymerization en masse is done directly in the
space of the tube by adding one 10 .mu.L drop of the reaction
mixture defined at the beginning of the example. The system
obtained is sulfonated using trimethylsilylchlorosulfonate, 2 moles
per kilogram of copolymer with an excess of 10 mole % in a glove
box for a period of 12 hours by placing one 10 .mu.L drop of the
sulfonation agent on the microporous silicon material. The systems
obtained in this fashion were left for one hour in the open air,
then washed in distilled water for a period of 12 hours in order to
obtain sulfonates.
EXAMPLE 36
[0165] A series of samples of initial compositions in moles of
TEOS.sub.n-PTES.sub.(1-n) (with n=0.1, 0.4, 1) was synthesized
using as the catalyst NH.sub.4F after hydrolysis of half of the
ethoxy groups. After 48 hours of reaction at room temperature, the
supernatant solution was removed. The precipitate was collected in
dichloromethane. The 0 and 20% TEOS samples did not, with the
exception of NH.sub.4F, produce any product insoluble in
CH.sub.2Cl.sub.2 and there was 40% of insoluble product in the
dichloroethane for the 40% samples. For the 40% samples, the
insoluble fractions were washed in methanol and the same method was
used for pure TEOS. Two 40% TEOS samples, one 10% TEOS sample and
pure TEOS were synthesized using the same catalyst. After
polycondensation over a period of 48 h at 60.degree. C. in the
oven, the PTES/TEOS (90/10) and PTES/TEOS (60/40) samples were
sulfonated by chlorosulfonic acid, which is introduced typically in
the stoichiometry of 20% relative to PTES in dichloromethane. All
of the products were immediately precipitated in the solvent. The
results of testing of good or unsatisfactory solvents of sulfonated
BTES/TEOS (90/10) are given in the following table 5:
5 TABLE 5 Good Solvents Non-Solvents Ethyl alcohol Water 25.degree.
C. N,N-dimethylformamide dimethyl Dichloroethane acetal Methyl
sulfoxide Boiling water
[0166] 40% sulfonated PTES/TEOS does not dissolve in water, ethyl
alcohol, dichloromethane, methyl alcohol and acetone. 40%
sulfonated PTES/TEOS does not dissolve in water, ethyl alcohol,
dichloromethane, methyl alcohol and acetone. Concentrated solutions
of 10% sulfonated PTES/TEOS in the different good solvents were
introduced into the space of the microporous silicon material by
capillary action by depositing a 10 .mu.L drop. The systems
obtained in this fashion were left for one hour in the open air,
then washed in distilled water for a period of 12 hours. For 40%
PTES/TEOS, copolymerization en masse is done directly in the space
of the tube by adding one 10 .mu.L drop of the reaction mixture
defined at the beginning of the example. The system obtained is
sulfonated using trimethylsilylchlorosulfonate, 2 moles per
kilogram of copolymer with an excess of 10 mole % in a glove box
for a period of 12 hours by placing one 10 .mu.L drop of the
sulfonation agent on the microporous silicon material. The systems
obtained in this fashion were left for one hour in the open air,
then washed in distilled water for a period of 12 hours in order to
obtain sulfonates.
EXAMPLE 37
[0167] A polybenzylsilsesquioxane based on BTES was synthesized
using NH.sub.4F as the catalyst in the lumen of the microporous
silicon material by placing one 10 .mu.L drop of BTES with the half
of its ethoxysilane hydrolysates and the catalyst. The silicon was
previously oxidized to create surface silanols. Condensation was
then done initially between the surface silanols and the BTES
ethoxysilane and then between the BTES silanols and its
ethoxysilane groups. The polyBETS formed is chemically linked to
the wall of the microporosities and thus insoluble in the solvents.
After 48 hours of reaction at room temperature, polycondensation is
terminated by 48 hours of heating at 60.degree. C. in an oven and
then the system is washed in distilled water for a period of 24
hours. The microporous material is dried under vacuum at
100.degree. C., then sulfonated using
trimethylsilylchlorosulfonate, 3 moles per kilogram of copolymer
with a 10 mole % excess, in the glove box over a period of 12 hours
by placing a 10 .mu.L drop of the sulfonation agent on the
microporous silicon material. The systems obtained in this fashion
are left for one hour in the open air, then washed in distilled
water for a period of 12 hours in order to obtain the sulfonic acid
groups. The protonic conductivity measured at 25.degree. C. under
90% relative humidity is 50 mS/cm.
EXAMPLE 38
[0168] A phenylsilsesquioxane based on PTES was synthesized using
NH.sub.4F as the catalyst in the lumen of the microporous silicon
material by placing one 10 .mu.L drop of PTES with half of its
ethoxy hydrolysates and the catalyst. After 48 hours of reaction at
room temperature, polycondensation is terminated by 48 hours of
heating at 60.degree. C. in an oven and then the microporous
material is washed in distilled water for a period of 24 hours. The
system is dried under vacuum at 100.degree. C., then sulfonated
using trimethylsilylchlorosulfo- nate, 2 moles per kilogram of
copolymer with a 10 mole % excess, in the glove box over a period
of 12 hours by placing a 10 .mu.L drop of the sulfonation agent on
the microporous silicon material. The systems obtained in this
fashion were left for one hour in the open air, then washed in
distilled water for a period of 12 hours in order to obtain
sulfonates.
[0169] Second Preferred Embodiment.
[0170] In the first embodiment, the conduction of the protons can
be approximated by the conductivity of the channels constituted by
the three dimensional polymer chains. In the second preferred
embodiment, the active surface for electrochemical exchanges is
raised, by bonding the molecules to the inner surfaces of the
channels.
[0171] Here is described an example of a method to obtain a
membrane according to the second preferred embodiment.
[0172] The different steps of the method are as follows, and are
shown in FIG. 11 and FIG. 12.
[0173] In the first step 111 of FIG. 11, shown as well in FIG.
12(a), an N-type blank wafer 120 of silicon is prepared. The wafer
120 is <100> oriented, and the resistivity of the wafer 120
is from 0.02 _.cm for example.
[0174] In step 112, the wafer 120 is oxidized by a thermal
oxidizing, in an oven, at a temperature of 1000.degree. C. for
instance. A flux of oxygen and water vapour flows in the oven has.
The resulting layer of silicon oxide is referred to as 121 in FIG.
12(b).
[0175] In step 113 shown in FIG. 12(c), a layer 122 of chromium is
coated on each surface of the wafer. The coating is conducted by
cathodic spraying. The layer 122 has for example a thickness of 150
nm. This layer 122 serves as a layer of hanging-up for a layer 123
of gold. The layer of gold is for instance 1 .mu.m-thick. The
coating of the gold layer 123 is made thanks to a cathodic spraying
as well.
[0176] In step 114, a photolithography is realised on the wafer
120, which has been metallized in step 113. The photolithography is
realised on each of the surface thanks to a chromed glass mask. A
photosensitive resin 124 is firstly coated on the wafer 120, above
the gold layer 123, as shown in FIG. 12(d). The patterns of the
mask are then reproduced by exposure of the resin 124 to
ultraviolet radiation. The exposed parts of the resin 124 are then
removed in an adapted solvent. The metal layer 123 is therefore
bare on the desired locations for the membranes.
[0177] In step 115, the bare patterns are then etched by adapted
etching solutions. The layers of gold, chromium are etched. The
result of the etching of the metal layers 122 and 123 is shown in
FIG. 12(e). The silicon dioxide is then etched as well in an
ammonium bifluoride (BHF) solution (7 vol. NH.sub.4F 40%+1 vol HF
50%). The result of such an etching is shown in FIG. 12(f). The
etching of the silicon membranes is done is a KOH solution, with a
concentration of 41%. A 40 .mu.m-thick membrane 125 is obtained in
FIG. 12(g). The resin is removed at that stage.
[0178] In step 116, the drilling of the membrane 125 is done so as
to make the membrane 125 porous. The drilling is made by classic
anodisation. The container in which anodisation is conducted is a
double tank container. The bath is composed of HF:ethanol. The
proportions of each component can be, for instance, 1:1. The result
of the drilling is shown in FIG. 11(h). The concentration of the HF
is for instance 48%.
[0179] In a step 117, the aim is to open all the channels 126. At
the end of step 116, all the channels 126 may not be open, as it is
shown in FIG. 12(h) where some channels 126 are blocked by the wall
127. To reach such an aim, a plasma reactive etching is conducted
on the rear surface of the wafer. Such an etching allows the
removal of material off the wall 127 on a few hundreds of nm. All
the channels 126 are then open, as it is shown in FIG. 12(i).
[0180] In step 118, the channels 126 are then made hydrophilic
thanks to two successive treatments. The membrane 125 is firstly
put in a solution containing 80% of sulphuric acid and 20% of
hydrogen peroxide. The membrane stays in the solution during around
60 minutes. Secondly, the membrane is put in a container where each
surface is exposed to ultraviolet rays and an ozone flux. The
exposure of each surface lasts around 10 minutes.
[0181] In step 119, molecules (an acid silane for example) are
bonded to the surfaces of the channels 126. The membrane is put in
an acid silane solution to a concentration of 1% during 60 minutes
for example.
[0182] More generally, FIG. 13 is a schematic representation of the
steps for the filling of channels by the proton conductive
material. In FIG. 13, the channels 131 are drilled in the membrane
130 according to the method of anodisation just described
above.
[0183] As for the first preferred embodiment as well, the proton
conductive material 134 is introduced in the channels 131 of a
membrane 130 under the form of a molecule or monomer. The molecule
or monomer material 134 has different kinds of chemical groups. The
monomers or molecules have on the one hand a "head" part 132 that
can be bonded to the surface of the channels 131, and on the other
hand a "tail" part 133 that is proton conductive. The typical size
of the channels adapted to bonded molecules or monomers is under 10
nm and can be of the order of magnitude of 1 to 3 nm. It can be
seen that the diameter of the channels is greatly reduced.
[0184] The active surface of the polymer is yet raised. The active
surface for the conduction is now the whole inner surface of the
channels 131, since it is coated with the proton conductive tails
133. Tails 133 are free to move in the channels 131. The
conductivity of the membrane 130 is therefore greatly improved.
[0185] The monomer 134 that is introduced in the channels 131 is
silicon compound.
[0186] The chemical bonding of active molecules on the inner
surface of the channels of the porous silicon is now described.
[0187] The native layer of silicon dioxide in the channels 131 must
have a sufficient thickness to allow the bonding of the monomer
molecules. The chemical bonding is possible if the surface of the
silicon dioxide has OH groups. The OH groups can be obtained on the
surface of the silicon dioxide in the channels 131 if the membrane
is put in a solution containing sulphuric acid and hydrogen
peroxide, during 60 minutes for instance.
[0188] As already mentioned, the chemical molecules bonded on the
inner surface of the channels 131 are silicon compounds having acid
groups COOH, such as an acid silane
(N-[trimethyloxysilylpropylethylenediamine] triacetic acid) or
sulfonic groups (SO.sub.3H), such as benzyltriethoxysilane after
sulphonation.
[0189] During the bonding, the H of the OH group is removed from
the channel surface, and an OR group of a silicon compound molecule
(SiOR) is removed. Alcohol is formed when the two removed groups
combine. A covalent bonding is formed between in the one hand the
silicon compound and on the other hand the surface.
[0190] As most of the inner surface of the channels 131 is coated,
the diameter of the channels 131 can be reduced without affecting
the conduction active surface. The reduced diameters of the
channels improve the tightness of the membrane to the fuel and
oxidant.
[0191] Referring to FIG. 11 again, in step 1190, a thin layer of
platinum is coated by cathodic spraying on each surface of the
membrane. The thickness of the layer is equal to 1 to 2 nm. Each
layer is therefore an electrode and a catalyst.
[0192] Now examples of molecules that can be used in the second
preferred embodiment will be described.
[0193] On can use a monomer having the general formula
Si(Cl).sub.n(CH.sub.2).sub.x(C.sub.6H.sub.5).sub.4-n or the formula
Si(OR).sub.n(CH.sub.2).sub.x(C.sub.6H.sub.5).sub.4-n, where x can
assume the values of 0 to 8 but preferably from 0 to 4, n can vary
between 1 and 3, preferably between 2 and 3, R is an alkyl group of
the general formula: C.sub.nH.sub.2n+1. After condensation, total
or partial, of the monomer with the surface silanols, the
sulfonation reagent enabling substitution of the aromatic ring(s)
by one or a plurality of sulfonic groups is introduced.
[0194] Examples 39 to 41 show the application of such
molecules.
EXAMPLE 39
[0195] Surface hydroxyls are created on the space of the
microporous silicon material under ozone and ultraviolet. One 10
.mu.L drop of BTES is placed on the silicon microporous material so
that it wets the porosity by capillary action and it condenses on
the space with the surface hydroxyls. After 48 hours of reaction at
room temperature, polycondensation is terminated by 48 hours of
heating at 60.degree. C. in an oven and then the microporous
material is washed in distilled water for a period of 24 hours. The
system is dried under vacuum at 100.degree. C., then sulfonated
using trimethylsilylchlorosulfonate, 2 moles per kilogram of
copolymer with a 10 mole % excess, in the glove box over a period
of 12 hours by placing a 10 .mu.L drop of the sulfonation agent on
the microporous silicon material. The systems obtained in this
fashion were left for one hour in the open air, then washed in
distilled water for a period of 12 hours in order to obtain
sulfonates.
EXAMPLE 40
[0196] The purpose of this example is to functionalize the exposed
surface in the microporous material with PTES then to sulfonate the
aromatic rings. Surface hydroxyls are created on the space of the
microporous silicon material under ozone and ultraviolet. One 10
.mu.L drop of PTES is placed on the silicon microporous material so
that it wets the porosity by capillary action and it condenses on
the space with the surface hydroxyls. After 48 hours of reaction at
room temperature, polycondensation is terminated by 48 hours of
heating at 60.degree. C. in an oven and then the microporous
material is washed in distilled water for a period of 24 hours. The
system is dried under vacuum at 100.degree. C., then sulfonated
using trimethylsilylchlorosulfonate, 2 moles per kilogram of
copolymer with a 10 mole % excess, in the glove box over a period
of 12 hours by placing a 10 .mu.L drop of the sulfonation agent on
the microporous silicon material. The systems obtained in this
fashion were left for one hour in the open air, then washed in
distilled water for a period of 12 hours in order to obtain
sulfonates.
EXAMPLE 41
[0197] Surface hydroxyls are created on the space of the
microporous silicon material under ozone and ultraviolet. One 10
.mu.L drop of BTES/PTES (25/75; 50/50 and 75/25 in moles) is placed
on the silicon microporous material so that it wets the porosity by
capillary action and condenses on the space with the surface
hydroxyls. After 48 hours of reaction at room temperature,
polycondensation is terminated by 48 hours of heating at 60.degree.
C. in an oven and then the microporous material is washed in
distilled water for a period of 24 hours. The system is dried under
vacuum at 100.degree. C., then sulfonated using
trimethylsilylchlorosulfonate, 2 moles per kilogram of copolymer
with a 10 mole % excess, in the glove box over a period of 12 hours
by placing a 10 .mu.L drop of the sulfonation agent on the
microporous silicon material. The systems obtained in this fashion
were left for one hour in the open air, then washed in distilled
water for a period of 12 hours in order to obtain sulfonates.
[0198] According to other embodiments, OH groups are still
eliminated after the filling of the channels.
[0199] It is possible to simultaneously introduce into the porosity
monomers of the
Si(Cl).sub.n(CH.sub.2).sub.x(C.sub.6H.sub.5).sub.4-n or of the
Si(OR).sub.n(CH.sub.2).sub.x(C.sub.6H.sub.5).sub.4-n type with the
same assumption for x and n as in examples 39 to 41 and other
monomers of the Si(Cl).sub.n-R.sub.4-n' or Si(OR).sub.nR.sub.4-n'
type, wherein R' can be an alkyl CnH2n+1 or alkenyl CnH.sub.2n-1.
After condensation, total or partial, of the monomer with the
surface silanols, the sulfonation reagent enabling substitution of
the aromatic ring(s) by one or a plurality of sulfonic groups is
introduced.
[0200] Examples 42 and 43 show the application of such
molecules.
EXAMPLE 42
[0201] Surface hydroxyls are created on the space of the
microporous silicon material under ozone and ultraviolet. One 10
.mu.L drop of BTES is placed on the silicon microporous material so
that it wets the porosity by capillary action and it condenses on
the space with the surface hydroxyls. After 48 hours of reaction at
room temperature, polycondensation is terminated over a period of
48 hours at 60.degree. C. in an oven then the uncondensed hydroxyls
are fixed by the addition of a drop of ClTMS on the microporous
material, which is then washed in distilled water over a period of
24 hours. The system is dried under vacuum at 100.degree. C., then
sulfonated using trimethylsilylchlorosulfo- nate, 2 moles per
kilogram of copolymer with a 10 mole % excess, in the glove box
over a period of 12 hours by placing a 10 .mu.L drop of the
sulfonation agent on the microporous silicon material. The systems
obtained in this fashion were left for one hour in the open air,
then washed in distilled water for a period of 12 hours in order to
obtain sulfonates.
EXAMPLE 43
[0202] Surface hydroxyls are created on the space of the
microporous silicon material under ozone and ultraviolet. One 10
.mu.L drop of PTES is placed on the silicon microporous material so
that it wets the porosity by capillary action and it condenses on
the space with the surface hydroxyls. After 48 hours of reaction at
room temperature, polycondensation is terminated over a period of
48 hours at 60.degree. C. in an oven then the uncondensed hydroxyls
are fixed by the addition of a drop of ClTMS on the microporous
material, which is then washed in distilled water over a period of
24 hours. The system is dried under vacuum at 100.degree. C., then
sulfonated using trimethylsilylchlorosulfo- nate, 2 moles per
kilogram of copolymer with a 10 mole % excess, in the glove box
over a period of 12 hours by placing a 10 .mu.L drop of the
sulfonation agent on the microporous silicon material. The systems
obtained in this fashion were left for one hour in the open air,
then washed in distilled water for a period of 12 hours in order to
obtain sulfonates.
[0203] Third Preferred Embodiment.
[0204] FIG. 14 represents schematically another embodiment of the
present invention. In this embodiment, the membrane 140 is similar
to the membranes of the other preferred embodiments, and the
channels 141 are drilled by anodisation, as in the second preferred
embodiment for instance. The monomer 144 that is introduced in the
channels 141 is of the same type as the monomer introduced in the
second preferred embodiment. It has a head that can be bonded to
the inner surface of the channels 141 and a tail that can conduct
protons. The monomer 144 that is introduced in the channels 141 is
a silicon compound having acid groups (COOH) or SO.sub.3H (obtained
by sulphonation). The examples 39 to 43 can be referred to as well
to define the molecules that can be used in the embodiment.
[0205] The difference between the third preferred embodiment and
the second preferred embodiment is that, in the third preferred
embodiment, the tails of the molecules of monomers are cross-linked
after being bonded as it is shown is channel 142.
[0206] The cross-linking is made thanks to the use of heat and/or
catalysts in the solution.
[0207] Therefore, the material in the channels 142 is still proton
conductive, but the channels 142 are blocked by the cross-linking
of the tails of the molecules. Therefore, the tightness of the
membrane to the fuel and/or the fuel oxidant is raised. It is
specifically true with if the fuel is an alcohol.
[0208] After the steps of cross-linking, the steps for the making
of the electrodes and the catalysts are still the same as for the
other embodiments.
[0209] Generalization.
[0210] In the above-mentioned examples, the method for anodisation
in the method for making the first preferred embodiment is
applicable as well to the method for making the second or third
preferred embodiment, and reciprocally.
[0211] Of course, any combination of the embodiments for the
membrane is possible. A first example is that a long polymer can be
introduced in the channels after a monomer has been introduced. The
monomer can be therefore cross-linked to the polymer and/or to the
monomers as wanted. According to a second example, molecules and/or
monomers can also be bonded to the inner surface of the channels,
and a polymer and/or monomer can be introduced in the channels
after that. The bonded molecules and/or monomers can be
cross-linked to each other and/or to the polymer and/or to the
monomer as wanted. According to a third example, a polymer and/or a
monomer can be introduced in channels where molecules are bonded
and crossed-linked already. The monomers can be cross-linked
between them and/or to the bonded and cross-linked polymers. It is
understood that a man skilled in the art will imagine other
possibilities that the three cited examples, without leaving the
scope of the invention.
[0212] The preferred embodiments refer only to the making of the
membrane and do not refer to the structure of the cell. That means
that the membrane can be as shown in FIG. 4a. The membrane is
constituted at the level of the cell elements 5 by a complex of
basic membranes 12 separated by metal layers 13, the whole being
passed through by micro-channels 11 which ensure the passage of the
protons. The preferred embodiments of the membrane can be in a cell
or an apparatus according to FIGS. 1 to 6.
* * * * *